When installing solid fuel stoves, it’s important to make sure there’s sufficient air supply to enable the safe and proper operation of the appliance and its connecting flue system.
Contributing factors include the kW output of the stove, the age of the building, whether a flue draught stabiliser is installed/to be installed, and whether the building fabric has been substantially upgraded. It’s worth considering that due to increased energy efficiency requirements in regional building regulations, it’s unlikely that dwellings built before 2008 would have air permeability (air tightness) of equal to or less than 5.0 m3 / (h.m2) at 50 Pa.
So, let’s look at the requirements, broken down to whether or not a draught stabiliser is installed, and the regional differences.
Without a draught stabiliser
In regions except the Republic of Ireland, if you were to install a stove with a rated output of no greater than 5kW and the property’s design air permeability is greater than 5.0 m3 / (h.m2) with no draught stabiliser installed, there would not be a requirement to provide a permanent air vent to bring air supply to the stove. However, if the rated output of the stove was in excess of 5kW, then provision would need to be made to provide air supply giving a minimum 5.5cm2 per kilowatt of the rated output above 5kW. For example, a 6kW stove would require an air supply of a minimum 5.5cm2.
Where the design air permeability is equal to or less than 5.0 m3 / (h.m2), air supply will need to be provided offering a minimum 5.5cm2 per kW., whatever the appliance rated output.
In the Republic of Ireland, when installing a stove with no draught stabiliser and the property’s air permeability is greater than 5.0 m3 / (h.m2), provision would need to be made to provide air supply which meets one of the following requirements. You would need to provide whichever is the greater of 65cm2 or 5.5cm2 per kW of the appliance rated output.
Where the air permeability is equal to or less than 5.0 m3 / (h.m2) then the air supply would need to be provided offering 65cm2 plus 5.5cm2 per kW of the appliance rated output above 5kW.
With a draught stabiliser
Additional combustion air supply is required where draught stabilisers are installed. In regions except the Republic of Ireland, where the design air permeability is equal to or less than 5.0 m3 / (h.m2), then the air supply would need to provide 8.5cm2 per kW of the appliance rated output. When the design air permeability exceeds this, 3cm2 per kW will need to be provided for the first 5kW of the appliance rated output and then an additional 8.5cm2 per kW for the remaining balance. In the Republic of Ireland, where a draught stabiliser is installed, the information given in without a draught stabiliser is to be followed with the addition that a further 3cm2 per kW of the appliance rated output is also to be provided.
Image supplied by OFTEC
